The present invention relates generally to the field of anti spinning devices for vehicles, and more specifically to an anti spinning device for a work vehicle.
The invention also relates to a method for controlling such an anti spinning device.
The invention is applicable to all kind of vehicles equipped with ground engagement elements, e.g. wheels, that are sensitive to be damaged if they are allowed to spin on a rough surface. However, a preferred application is for work vehicles, e.g. wheel loaders, backhoe loaders, and the like, having rubber tires.
Work vehicles, e.g. a wheel loader, running slowly on a low gear during a working procedure, such as a loading procedure of the bucket, has a great torque transmitted to the ground engagement elements. If the propulsion of the work vehicle is obstructed by an external element and the wheels does not have sufficient grip to overcome the external force, the wheels run the risk of spinning due to the great torque transmitted to them. If one of the wheels spin, the great torque built up in the converter of the vehicle suddenly drops and the torque is lost for all wheels. At the same time the spinning wheel run the risk of being cut to pieces or punctured if the surface is rough and full of sharp or pointed stones. Since the wheels on work vehicles are quite large and expensive it is costly for the contractor each time a wheel is damaged, due to material costs as well as troublesome maintenance.
Today the contractor is totally dependent on the driving skills of the operators of the work vehicles. Even though the operators are well experienced, they may misjudge the nature of the ground and cause the tires severe damages by unintentional spinning. The operator is forced to know when to step off the accelerator, more precisely he/she has to step off the accelerator in the time span between the vehicle stops to move and the wheels starts to spin. Most times these two things appear at the same time, which makes it impossible to succeed.
One known way of trying to solve the problem of damaged tires due to unintentional spinning, is to brake the wheel that has started to spin, as soon as possible after detection of spinning taking place. But this method of trying to reduce the damages on the tires is too slow. The wheel has already rotated enough for the tyre to be cut into pieces or punctured. At the same time almost all of the torque that was built up in the converter is used up upon spinning, as mentioned above. One way of reducing the probability for unintentional spinning is to use a differential lock forcing each pair of wheels to rotate jointly, but this is not a preferred option on articulated vehicles since it may be quite large differences between the rotational speed of the inner wheel and that of the outer wheel upon turning. The use of a differential lock result in that both the differential lock itself and the tires are stressed. At the same time as the function of the differential lock as an anti spinning device is pore and random, since both wheels may spin together.
The present invention aims at obviating the aforementioned disadvantages of previously known anti spinning devices, and at providing an improved anti spinning device. It is desirable to provide an improved anti spinning device of the initially defined kind. It is also desirable to provide an anti spinning device, which ensure that the tires are spared by not being able to spin. It is also desirable to provide an anti spinning device, which ensures that the built up torque in the converter of the vehicle does not suddenly drop as a consequence of unintentional spinning. It is desirable to provide an anti spinning device, which is not dependent on the driving skills of the operator.
According to an aspect of the invention an anti spinning device comprises means for detecting the fulfillment of a preset condition and means for interrupting the power transmission to the individual rotatable element when the preset condition is fulfilled. Said condition is preferably related to the operation of the rotatable element.
According to an aspect of the present invention, there is provided an anti spinning device of the initially defined kind, in which the means for interrupting the power transmission comprises a braking system for braking a rotation of the rotatable element. Said braking system may comprise an individually controlled brake device for each rotating element.
According to another aspect of the invention, a method comprises the step of transmitting power to at least one rotating element in a vehicle driveline, and repeatedly interrupting the power transmission to the individual rotating element when a preset condition is fulfilled. Said condition is preferably related to the operation of the rotating element.
Thus, an aspect of the present invention is based on the insight of the importance of having an arrangement that may control each wheel independently regarding propulsion, braking and movement monitoring, and by means of this synchronize the rotation/position of the wheels. More precisely, each wheel is not allowed to rotate more than a predetermined angle before all wheels have rotated that predetermined angle, and then it recommence and each wheel is not allowed to rotate more than the predetermined angle before all the wheels have rotated the predetermined angle.